The present disclosure relates to tools for compressing or crimping a stented prosthesis. More particularly, it relates to tools and methods for progressively reducing the outer profile of a stented prosthesis, for example a stented prosthetic heart valve.
Stents are cylindrical-shaped devices that are radially expandable to hold open a segment of a vessel or other anatomical lumen after implantation into the lumen. Various types of stents are in use, including expandable and self-expanding stents. Expandable stents generally are conveyed to the area to be treated on balloon catheters or other expandable devices. For a self-expanding stent, commonly a sheath is retracted, allowing expansion of the stent.
Bioprosthetic stent devices are employed in a variety of surgical treatments. For example, a stent can be designed for use in counteracting restenosis, or the repeated narrowing of a blood vessel. In other applications, a stent can be utilized as part of a stented prosthetic heart valve. A stented heart valve prosthesis employed with catheter-based, or transcatheter, procedures generally includes an expandable multi-level frame or stent that supports a valve structure having a plurality of leaflets. The frame can be contracted during percutaneous transluminal delivery, and expanded upon deployment at or within the native valve. One type of valve stent can be initially provided in an expanded or uncrimped condition, then crimped or compressed about a balloon portion of an inner catheter or inner shaft. The balloon is subsequently inflated to expand and deploy the prosthetic heart valve. With other stented prosthetic heart valve designs, the stent frame is formed to be self-expanding. With these systems, the valved stent is crimped down to a desired size over an inner shaft and held in that compressed state within an outer sheath for transluminal delivery. Retracting the sheath from this valved stent allows the stent to self-expand to a larger diameter, fixating at the native valve site. In more general terms, then, once the prosthetic valve is positioned at the treatment site, for instance within an incompetent native valve, the stent frame structure may be expanded to hold the prosthetic valve firmly in place. One example of a stented prosthetic valve is disclosed in U.S. Pat. No. 5,957,949 to Leonhardt et al., which is incorporated by reference herein in its entirety.
Regardless of design (e.g., expandable or self-expanding) and end-use application, a stented prosthesis is normally collapsed or crimped to a smaller profile by a specialized tool for placement on or in the corresponding delivery device. For example, tools incorporating a conical- or funnel-shaped loading device are known. With these tools, the stented prosthesis is pulled or otherwise directed through the funnel-shaped device, forcing the stent to collapse to a reduced diameter profile. Alternatively, crimping tools are known that include a plurality of segments or jaws arranged to define a chamber (e.g., an iris type camber, a star-type chamber, or other geometric configuration) and translatable relative to one other in selectively reducing a size of the chamber (and thus a profile a stented prosthesis located within the chamber).
With many stent-based surgical procedures, it is desirable to affect as small a profile as possible into the stented prosthesis for delivery to the target site so as to minimize invasiveness of the procedure and enhance patient safety. While generally viable, existing compression tools are unable to effectuate desired profile reductions in some stented prosthetic devices, such as self-expanding stented prosthetic heart valves. Further, existing compression tools oftentimes generated bulges, or bumps or other non-uniformities in the collapsed stented prosthesis; these non-uniformities are undesirable as they can “catch” on human anatomy while being tracked to the target site.